Device comprising an electric discharge tube having a concentrated electron beam



p 11, 1956 A. J. w. M. VAN OVERBEEK 2,762,916

DEVICE COMPRISING AN ELECTRIC DISCHARGE TUBE HAVING A CONCENTRATEDELECTRON BEAM Filed June 30. 1951 ADRIANUS JOHANNES WILHELMUS MAm a r iRBEEK AGENT DEVICE COMPRISING AN ELECTRIC DISCHARGE HAVENG A'CONCENTRATED ELECTRON BEAM Adrianas Johannes Wilhelmus Marie vanOverbeek, Eindhaven, Netherlands, assignor to Hartford National Bank andTrust Company, Hartford, Conn., as trustee Application June 30, 1951,Serial No. 234,485 Ciainzs priority, application Netherlands July 13,'1950 1 Claim. (Cl. 250-27) This invention relates to a devicecomprising an electron discharge tube having a concentrated electronbeam through the use of which a very high mutual conductance can bedeveloped in a simple manner.

it has previously been suggested to increase the sensitivity ofdeflection control of a tube by means of a space charge developedbetween the beam and the deflection electrode, the deflection due to thedeflection electrode being assisted by the space charge. Such anincrease was attained by making improvements in the deflection controlitself in a tube having a double control. In addition, it has been foundpossible to utilize the influence of space charge to ensure a very highmutual conductance even in the case of intensity control, if theelectron beam is directed upon any of the collecting electrodes only asa result of space charges formed by the beam current itself inaccordance with the intensity of the beam. The deflection of theelectron beam due to these space charges, which was formerly found to begenerally undesirable, is now used to direct a portion of the beam awayfrom given collecting electrodes and onto a further collectingelectrode. The last-mentioned collecting electrode forms, in general,the anode. The intensity of the beam is controlled by the controlelectrode so that increasing the beam intensity increases the intensityof that portion of the electron beam directed upon the collecting anodereferred to. In addition, simultaneously with this increase in beamintensity a large portion of the beam is directed upon this electrode.The beam thus can be fully deflected in accordance with the controlledintensity of the beam without a separate deflection control.

The principle described can be realized with advantage with the use of adevice comprising an electric discharge tube having a concentratedelectron beam and an electrode system comprising at least a cathode, acontrol grid and two collecting electrodes, in which the beam can bedirected upon any one of the collecting electrodes only by the spacecharges which are formed by the beam itself in accordance with theintensity of the beam. In accordance with the invention, the beam ispassed into a cage maintained at a fixed low or zero potential so thatat a low beam intensity the electrons strike a collecting electrodearranged at the back of the cage, whereas with increasing beam intensitythe beam is reflected to a further collecting electrode because of thespace charge produced in the cage.

Thus, with low beam intensity, the beam passes through the cage to acollecting electrode arranged at the back of the cage, whereas in thecase of a high current strength the space charge set up in the cage issuch that the beam is substantially reflected thereby to a furthercollecting electrode, arranged more or less laterally of the cage.

In order that the invention may be more clearly understood and readilycarried into efiect, it will now be described more fully with referenceto the accompanying drawing, in which Fig. 1 shows diagrammatically oneembodiment of a tube suitable for use in a device according to theinvention, and

ted States Patent Fig. 2 shows the IaVg characteristic curve of such atube.

Referring to Fig. 1, the cathode is designated 1, the intensity controlelectrode 2 and a screen 3. The control electrode 2 may comprise smallscreens so that the electron fiow is concentrated to form a beam but, asan alternative, separate beam-forming electrodes 14 may be arranged.Referring to Fig. 1, use is made of a straight beam, which, in the caseof a low current strength passes through a cage 9 and then reaches acollecting electrode 10. The cage 9 is at a fixed low voltage or at zeropotential so that with increasing beam current a space charge is set upin the cage by which an increasing portion of the electron beam isreflected to an output anode 11 connected to an output circuit 12. Inthis case a high mutual conductance is obtained for the said anode.

Fig. 2 shows the IaVg characteristic curve of a normal tube which hasonly intensity control without the use of space charge deflection (curve1). Curve II is the Ia-Vg characteristic curve of a similar tube inwhich space charge deflection is used. It clearly shows the intenseincrease in mutual conductance, the advantage being that the latter isobtainable without very accurate electrode machining or very smallelectrode spacmgs.

Obviously, still further embodiments are possible without departing fromthe scope of the invention.

What I claim is:

A circuit arrangement comprising an electric discharge tube having beamproducing means including a cathode and control electrode and means forproducing a concentrated electron beam in a given path of an intensitysufficient to establish a space charge in a field-free region, a firstcollecting electrode located in said given path, a second outputcollecting electrode disposed outside said given path to intercept aportion of said beam at higher intensities thereof, and a singlecage-like electrode disposed in said given path entirely between thecontrol electrode and the first collecting electrode and enclosing afield-free region; means to apply constant positive potentials relativeto said cathode to the collecting electrodes, means to apply to saidcage-like electrode a fixed potential between zero and a positive amountsmall relative to the potentials applied to the collecting electrodes tothereby establish a space charge within the region enclosed by thecage-like electrode, means to apply an input signal only to said controlelectrode to vary the intensity of said beam and thereby vary themagnitude of the space charge within the cage-like electrode and causethe beam to divide itself between the first and second collectingelectrodes in accordance with the intensity of the input signal, andmeans coupled to said second collecting electrode for deriving an outputsignal therefrom corresponding to the input signal applied to thecontrol electrode.

References Cited in the file of this patent UNITED STATES PATENTS2,220,840 Metcalf Nov. 5, 1940 2,256,301 Wagner Sept. 16, 1941 2,256,335Aldous et a1. Sept. 16, 1941 2,265,311 Preisach et a1 Dec. 9, 19412,271,985 Morton Feb. 3, 1942 2,273,546 Van Weel Feb. 17, 1942 2,284,829Ludi June 2, 1942 2,305,617 Hansell Dec. 22, 1942 2,332,876 Uhlmann Oct.26, 1943 2,569,971 Ballantyne Oct. 2, 1951

